I'll quote the petition for it here, just in case you don't want to bother to click the link:

Internet Service Providers (ISPs) are about to impose usage-based billing on YOU.

This means we're looking at a future where ISPs will charge per byte, the way they do with smart phones. If we allow this to happen Canadians will have no choice but to pay MUCH more for less Internet. Big Telecom companies are obviously trying to gouge consumers, control the Internet market, and ensure that consumers continue to subscribe to their television services.

These Big Telecom companies are forcing small competing ISPs to adopt the same pricing scheme, so that we have no choice but to pay these punitive fees.